Authors:Arkoprovo Biswas; Shashi Prakash SharmaPages: 439 - 455Abstract: Global optimization for the interpretation of Self-Potential (SP) anomaly using a very fast simulated-annealing (VFSA) inversion code is developed in the present study. The SP anomaly is measured over a 2-D inclined thick sheet-type electrostatically polarized structure. Different model parameters for thick sheet-type structures are optimized. VFSA optimization yields a large number of well-fitting solutions in a huge model space. Uncertainty in the interpretation is analyzed and the study shows that it remains in few model parameters. The efficacy of the developed approach has been demonstrated using noise free and noisy synthetic examples. Field data from three different regions is interpreted for multiple thick sheet-type structures related to mineral exploration. The computation time for finding this convenient solution is very short (100 s for single structure) and the proposed method is found to be useful for interpretation of thick sheet-type structure and for multiple bodies as well. The interpretation procedure can be used for assessing mineral deposits as well as the SP of the earth’s crust.PubDate: 2017-12-01DOI: 10.1007/s40328-016-0176-2Issue No:Vol. 52, No. 4 (2017)

Authors:Fridrich ValachPages: 457 - 465Abstract: This paper presents an analysis of the magnetic storm on March 8, 1918, on the basis of a preserved analogue magnetogram that was recorded by observatory Ógyalla, present day Hurbanovo. It is inferred that much of the spectacular phenomena that were attributed to this storm, such as effects in telegraph lines, were likely caused by rapid changes of the geomagnetic field during two consecutive substorms. The storm sudden commencement that preceded the magnetic storm was probably also potent in this regard. This supports the recent findings that argue against the inevitable major role of the ring current in extreme magnetic disturbances at mid latitudes.PubDate: 2017-12-01DOI: 10.1007/s40328-016-0177-1Issue No:Vol. 52, No. 4 (2017)

Authors:A. A. LyubushinPages: 467 - 478Abstract: The coherences between daily time series of four low-frequency seismic noise properties which were calculated for 78 broadband seismic stations of the network F-net in Japan and 81 broadband seismic stations in California for 13 years of observation, 2003–2015, is investigated. The studied time interval includes Tohoku mega-earthquake, M9, on March 11, 2011. The chosen noise properties are the following: minimum normalized entropy of squared wavelet coefficients, multifractal singularity spectrum support width, generalized Hurst exponent and index of linear predictability. These properties were estimated daily as median values taken over all stations of the networks. For each pair of these noise properties from Japan and California squared coherence spectrums were estimated within moving time window of the length 730 days. The maximum values of squared coherence spectra for periods more than 20 days were essentially increasing as the time window approaches the time moment of Tohoku mega-earthquake and achieved their maximum values for position of moving time window strictly before the seismic catastrophe. This fact is interpreted as a consequence of general global seismic noise synchronization before huge seismic catastrophe.PubDate: 2017-12-01DOI: 10.1007/s40328-016-0181-5Issue No:Vol. 52, No. 4 (2017)

Authors:Frank Neitzel; Burkhard SchaffrinPages: 479 - 496Abstract: The case of a singular dispersion matrix within the Gauss–Helmert Model has been considered before, most recently even allowing the rank of BQ to be smaller than the rank of B. In this contribution the emphasis is shifted towards an illuminating example, the 2D Helmert transformation.PubDate: 2017-12-01DOI: 10.1007/s40328-016-0184-2Issue No:Vol. 52, No. 4 (2017)

Authors:Annamária Kiss; Lóránt FöldváryPages: 497 - 510Abstract: Glacial ice mass balance of Antarctica can be observed by the twin satellites of the gravity recovery and climate experiment (GRACE). The gravity fields with monthly resolution enable efficient detection of annual, long periodic and secular variations. The present study delivers an error estimation of the long-periodic and secular variations by determining the linear trend of the observed surface mass anomaly series. Among the error sources, the error of the timing of the trend fitting, the error of the glacial isostatic adjustment correction, and the error of the atmospheric correction of the GRACE monthly solutions are discussed. The investigation concludes that apart from West Antarctica, Wilkes Land, Queen Maud Land and Enderby Land no reliable trend estimates of ice mass variation can be expected, thus any results should be treated with care.PubDate: 2017-12-01DOI: 10.1007/s40328-016-0185-1Issue No:Vol. 52, No. 4 (2017)

Authors:Robert Duchnowski; Zbigniew WiśniewskiPages: 511 - 525Abstract: The paper concerns assessing the accuracy of some variants of robust R-estimates, namely the Hodges–Lehmann estimates, which can be applied, for example, in deformation analyses. Such estimates are robust against outlying observations and in some cases they are a good alternative for more conventional methods of estimation, for example, in testing stability of the potential reference points. Considering such an application, or in general estimation of displacements of network points, one should of course know accuracy of the estimators. Since R-estimates are based on ranks it is not obvious how to compute their accuracy (the law of variance propagation cannot be applied here). This paper presents one of the possible approaches, namely application of Monte Carlo simulations. If we make certain assumptions concerning the distribution of observation errors, we can assess the accuracy of chosen R-estimates. Usually, we assume that the observation errors are normally distributed, however, we can also consider some distributions with positive or negative kurtosis, and in the latter case we may apply the system of Johnson’s distributions to simulate the observations. In the paper, the accuracy of R-estimates was computed in relation to the accuracy of LS estimates, which is advisable from a practical point of view. It turned out that the accuracy of R-estimates is a little bit worse than the accuracy of LS estimates in most of the cases. However, there are also some cases when R-estimates are more accurate, for example, for leptokurtic distributions of the observations. An example application of R-estimates in deformation analysis was also presented.PubDate: 2017-12-01DOI: 10.1007/s40328-016-0186-0Issue No:Vol. 52, No. 4 (2017)

Authors:Joanna Kuczynska-Siehien; Adam Lyszkowicz; Katarzyna Stepniak; Marta KrukowskaPages: 527 - 534Abstract: Results of three campaigns of Baltic Sea Level Project and further studies reveal the GPS and spirit levelling data possibly contain errors which affect SST and \( W_{0}^{L} \) computations. For that reason, the old data were revised and additionally, in spring 2015, the new GNNS campaign was carried out at tide gauges in Swinoujscie, Ustka and Wladyslawowo. The study concerns computation of the local average geopotential value \( W_{0}^{L} \) using water level data at the three tide gauges, geoid undulations from a global geopotential model EGM2008 and ellipsoidal heights from GNSS observations, which were obtained using revised data from three campaigns of Baltic Sea Level Project and from the new campaign conducted in 2015. Results obtained indicate that the best estimation of \( W_{0}^{L} \) was achieved from the campaign carried out in 2015, where the mean value of \( W_{0}^{L} \) calculated for three investigated tide gauge stations is equal to 62636857.45 m2 s−2.PubDate: 2017-12-01DOI: 10.1007/s40328-016-0188-yIssue No:Vol. 52, No. 4 (2017)

Authors:G. Sivavaraprasad; D. Venkata Ratnam; R. Sree Padmaja; V. Sharvani; G. Saiteja; Y. S. R. Mounika; P. Babu Sree HarshaPages: 535 - 553Abstract: The operational availability of Global Navigation Satellite System is affected by large-scale irregularities of the ionosphere. The space weather events induce several intense irregularities and cause the non-linear distribution of ionospheric electron density. Monitoring of ionospheric responses due to extreme space weather events plays a key role in trans-ionospheric radio wave propagation. In the present analysis, a novel technique based on wavelet transform has been implemented for the analysis and detection of ionospheric anomalies during two intense space weather events that occurred in 2013. The investigations have been carried out using the ionospheric observable, Total Electron Content (TEC), derived from the Global Positioning System (GPS) receiver located at an Equatorial Ionisation Anomaly region, KL University, Guntur, India (Geographic Lat.16.37°N, Geographic Long. 80.37°E). The effects of geomagnetic storms (Sym-H ≤ −100 nT) on the perturbations of ionospheric TEC have been investigated. The algorithm of Continuous wavelet transform has been used to study and characterise the presence of ionospheric anomalies in the local time-scale plane. It can detect spatial and temporal details of ionospheric anomaly intensity during strong solar-terrestrial and geophysical events. It is observed that during the main phase of the geomagnetic storm that occurred during 17 March 2013, TEC enhanced by 7 TECU, while a suppression of 10 TECU in the GPS-TEC can be noticed during the main phase of the 29 June 2013 storm. The variation in the intensity of ionospheric TEC anomalies during storm time has been detected and compared to the intensity of the space weather events measured through solar and geomagnetic indices (F10.7, Sym-H, IMF Bz and IEF Ey).PubDate: 2017-12-01DOI: 10.1007/s40328-016-0190-4Issue No:Vol. 52, No. 4 (2017)

Authors:Reza Ghanati; Hosseinali Ghari; Moslem FatehiPages: 555 - 580Abstract: In this paper we tackle the problem of inverting geophysical magnetic data due to simple shape anomalies caused by thin sheet, cylinder and fault models using Occam’s inversion scheme. A significant aspect of using Occam’s inversion is the choice of the regularization parameter controlling the trade-off between the data fidelity and regularization term in the cost function of optimization problem, and consequently, reliable estimation of subsurface models. Two criteria L-curve and weighted generalized cross validation are considered in order to choose an optimum value of the regularization parameter. The proposed strategy was first evaluated on three theoretical synthetic models for each of the magnetic simple-shaped structures with different random errors, where a considerable agreement was obtained between the exactly known and estimated models. The validity of the technique was also applied to one real data set from Morvarid iron-apatite deposit, in Northwest Iran. The resulting inverted parameters using the proposed algorithm correspond reasonably closely with the known geology and nearby borehole information.PubDate: 2017-12-01DOI: 10.1007/s40328-017-0193-9Issue No:Vol. 52, No. 4 (2017)

Authors:S. BarczaPages: 581 - 592Abstract: Radiative power balance of a planet in the solar system is delineated. The terrestrial powers are transformed to average global flux in an effective atmospheric column approximation, its components are delineated. The estimated and measured secular changes of the average global flux are compared to the fluxes derived from the Stefan–Boltzmann law using the observed global annual temperatures in the decades between 1880 and 2010. The conclusion of this procedure is that the radiative contribution of the greenhouse gas CO2 is some \(21\pm 7\) % to the observed global warming from the end of the nineteenth century excluding the feedback mechanisms playing determining role in the climate system. Stationary radiative flux transfer is treated in an air column as a function of the column density of the absorbent. Upper and lower limit of radiative forcing is given by assuming true absorption and coherent scatter of the monochromatic radiation. An integral formula is given for the outgoing long wave radiation as a function of column density of the components of greenhouse gases.PubDate: 2017-12-01DOI: 10.1007/s40328-016-0187-zIssue No:Vol. 52, No. 4 (2017)

Authors:Mehrdad Soleimani; Behshad Jodeiri Shokri; Mehrnoush RafieiPages: 283 - 299Abstract: Geological interpretation and seismic imaging on data acquired from complex media, especially when accompanied by a thick layer of salt and/or anhydrate, is always a controversial task. The aim of this study is to introduce a method for seismic imaging of complex structures and study the folding scenario of the Zagros overthrust in SW Iran based on the improved seismic image processed by the proposed method. A diffraction based version of the common reflection surface stack method, called the common diffraction surface (CDS), was selected to enhance quality of seismic image from the Zagros fold-thrust belt. The 2D CDS method was also developed here to 3D partial CDS. Consequently, three sets of 2D and a set of 3D seismic data were processed with the conventional Kirchhoff prestack time migration and the partial common diffraction surface methods. Geological models released in previous studies of the Zagros overthrust were used as the base model of interpretation. Structural interpretation on seismic sections with new method was in accordance with previous geological models and improved in some parts where the new method could enhance quality of the seismic image. Seismic structural interpretation shows the inner part of the belt was subjected to folding, uplift and erosion. This mechanism constituted a resistant mass in the Dezful Embayment in front of the SW moving thrust and folds. This resistant mass formed tightly folded or thrusted and highly shortened structures in the Izeh zone and High Zagros area. In the oil rich zone of the Dezful Embayment, the thick evaporate—rich Gachsaran Formation, decouples the folding above it from the folding below, making seismic imaging of potential traps beneath the detachment horizons extremely difficult.PubDate: 2017-09-01DOI: 10.1007/s40328-016-0182-4Issue No:Vol. 52, No. 3 (2017)

Authors:Shuai Zhou; Danian Huang; Jian JiaoPages: 317 - 329Abstract: Edge detection of the geological structures horizontal position is the vital task of the potential field interpretation, and some traditional edge detectors have poor ability in delineating edges clearly and accurately. Some people made efforts to purpose new methods which can balance the weak and strong anomalies simultaneously. In this paper, we purposed new edge detection methods based on directional total horizontal derivatives of three-dimensional structure tensor for the causative sources. In order to balance weak and strong amplitude anomalies simultaneously, we used the vertical derivatives of potential field to normalize the new defined filters. For the complex geological situation with positive and negative gravity or magnetic anomalies, we introduced a new strategy to reduce the false edges. The presented filters were tested on synthetic and real potential field data to verify its feasibility. All of the results have shown the new edge detection methods can not only display the sources edges precisely and clearly, but also bring out more geological subtle details.PubDate: 2017-09-01DOI: 10.1007/s40328-016-0171-7Issue No:Vol. 52, No. 3 (2017)

Authors:Tamás Bozóki; Mátyás Herein; Attila GalsaPages: 331 - 343Abstract: Numerical model calculations have been carried out to study the effect of the centrifugal force on the compositionally dense material accumulated in the lowermost mantle. The deformation of an initial dense layer encircling the core was investigated systematically as a function of the density difference between the lower dense and the overlaying mantle, β and the angular velocity of the planet, Ω in a two-dimensional cylindrical shell domain. It was established that increasing β does not influence the magnitude of the deformation of the dense layer but decreases the velocity of the deformation. The relaxation time of the deformation is inversely proportional to β similarly to post-glacial rebound. On the other hand, increasing Ω enhances the magnitude of the deformation but does not affect the deformation relaxation time. The magnitude of the deformation is approximately proportional to Ω2. It was pointed out that for the present-day mantle parameters, β = 2–4 % and Ω = 7.3 × 10−5 1/s the equatorial elevation of the dense layer is about 2 km which more than two orders of magnitude less than the height of the seismically observed large low shear velocity provinces beneath Africa and Pacific. During the Earth’s history when the rotation of our planet was faster the influence of the centrifugal force was much more significant and the equatorial elevation of the dense layer might have reached even 100 km.PubDate: 2017-09-01DOI: 10.1007/s40328-016-0172-6Issue No:Vol. 52, No. 3 (2017)

Authors:Salih Alcay; Cemal Ozer YigitPages: 345 - 356Abstract: This paper offers a comprehensive assessment of network-based positioning results using GPS-only and combined GPS/GLONASS data under open to limited sky view conditions. Data analysis is performed in a short (4 h) and a long (24 h) term spanning observations from five GNSS stations using 10°, 20°, 30° and 40° elevation cut-off angles, which simulate the availability of satellites in different sky view conditions. Evaluation of the results reveals insignificant differences between the accuracy of the GPS-only and combined GPS/GLONASS solutions for daily observation in all sky view conditions. However the clear advantage of integrating GPS and GLONASS observation in a GNSS differential solution is apparent for short (4 h) observation periods, particularly at the highest elevation cut-off angle (40°).PubDate: 2017-09-01DOI: 10.1007/s40328-016-0173-5Issue No:Vol. 52, No. 3 (2017)

Authors:Guoming Gao; Guofa Kang; Guangquan Li; Chunhua Bai; Yingyan WuPages: 407 - 420Abstract: In this paper, the magnetic model NGDC-720-V3 is used to investigate the distribution of crustal magnetic anomaly and the depth of Curie surface in west Himalayan syntaxis and its adjacent area. The Curie surface is compared with regional heat flow, the Moho, and seismicity. The results show that the magnetic anomaly and Curie surface are both consistent with the regional tectonic setting. Tarim craton, Tadjik Basin, and Indian Plate have positive magnetic anomaly and a Curie surface deeper than 36 km, corresponding to low heat flow there. In contrast, orogenic belts such as west Himalayan syntaxis, Tianshan Mountain, Afghanistan, and Tibetan Plateau have negative anomaly and a Curie surface shallower than 32 km, corresponding to high heat flow. The north of the syntaxis presents a positive anomaly on the surface, resulting from Ferghana Basin, while the negative anomaly in large depth is probably associated with the subduction of the slab and the resulting heat. The depth of the Curie surface has an inverse relationship to the Moho depth, which is attributed to temperature and isostatic balance. The distribution of earthquakes with epicenter deeper than 100 km clearly suggests the subduction of the Indian plate deep down to the asthenosphere and the deep earthquakes were caused by shear motion within the subducting slab.PubDate: 2017-09-01DOI: 10.1007/s40328-016-0179-zIssue No:Vol. 52, No. 3 (2017)

Authors:Gael Kermarrec; Steffen SchönAbstract: Least-squares estimates are unbiased with minimal variance if the correct stochastic model is used. However, due to computational burden, diagonal variance covariance matrices (VCM) are often preferred where only the elevation dependency of the variance of GPS observations is described. This simplification that neglects correlations between measurements leads to a less efficient least-squares solution. In this contribution, an improved stochastic model based on a simple parametric function to model correlations between GPS phase observations is presented. Built on an adapted and flexible Mátern function accounting for spatiotemporal variabilities, its parameters are fixed thanks to maximum likelihood estimation. Consecutively, fully populated VCM can be computed that both model the correlations of one satellite with itself as well as the correlations between one satellite and other ones. The whitening of the observations thanks to such matrices is particularly effective, allowing a more homogeneous Fourier amplitude spectrum with respect to the one obtained by using diagonal VCM. Wrong Mátern parameters—as for instance too long correlation or too low smoothness—are shown to skew the least-squares solution impacting principally results of test statistics such as the apriori cofactor matrix of the estimates or the aposteriori variance factor. The effects at the estimates level are minimal as long as the correlation structure is not strongly wrongly estimated. Thus, taking correlations into account in least-squares adjustment for positioning leads to a more realistic precision and better distributed test statistics such as the overall model test and should not be neglected. Our simple proposal shows an improvement in that direction with respect to often empirical used model.PubDate: 2017-10-31DOI: 10.1007/s40328-017-0209-5

Authors:Branislav Hábel; Juraj JanákAbstract: GOCE Level 2 products of corrected gravity gradients in Local North-Oriented Frame were used in this study. We analyzed four accurately measured elements of the gravity tensor, which were transformed to disturbing gravitational gradients. The investigation was carried out in the restricted region of dimension 20° × 20° covering the south part of Europe. We applied several types of analytical covariance functions in a local approximation, which have the best fit to the empirical covariances calculated from the disturbing gravitational gradients in particular sub-regions. At first, we have investigated four different types of the 1-dimensional covariance function. Obtained results show that the Gaussian covariance function approximates the empirical covariances the best from tested functions. Moreover, a time stability of calculated parameters of the covariance functions was studied by assuming GOCE data from different time periods. In the second experiment, we have compared two types of the 2-dimensional covariance function, which also enables a spatial stochastic modeling. The second study revealed that the least-squares collocation using the 2-dimensional local covariance function can produce the local grid of GOCE disturbing gravitational gradients directly from GOCE Level 2 products right below GOCE orbit, which in general fits well with the recent Earth’s global gravity field models and might have some advantages. Such local grids can be useful for specific tasks, e.g. mutual comparing of GOCE data collected during particular time periods.PubDate: 2017-10-31DOI: 10.1007/s40328-017-0208-6

Authors:Hang Yu; Jian Wang; Bin Wang; Houzeng Han; Guobin ChangAbstract: In this paper, a nonlinear dynamic errors-in-variables (DEIV) model which considers all of the random errors in both system equations and observation equations is presented. The nonlinear DEIV model is more general in the structure, which is an extension of the existing DEIV model. A generalized total Kalman filter (GTKF) algorithm that is capable of handling all of random errors in the respective equations of the nonlinear DEIV model is proposed based on the Gauss–Newton method. In addition, an approximate precision estimator of the posteriori state vector is derived. A two dimensional simulation experiment of indoor mobile robot positioning shows that the GTKF algorithm is statistically superior to the extended Kalman filter algorithm and the iterative Kalman filter (IKF) algorithm in terms of state estimation. Under the experimental conditions, the improvement rates of state variables of positions x, y and azimuth ψ of the GTKF algorithm are about 14, 29, and 66%, respectively, compared with the IKF algorithm.PubDate: 2017-10-17DOI: 10.1007/s40328-017-0207-7

Authors:Walyeldeen Godah; Malgorzata Szelachowska; Jan KrynskiAbstract: Temporal variations of geoid heights are vitally important in geodesy and Earth science. They are essentially needed for dynamic and kinematic updates of the static geoid model. These temporal variations, which substantially differ for different geographic locations, can successfully be determined using the Gravity Recovery And Climate Experiment (GRACE) mission data. So far, statistical decomposition methods, e.g. the Principal Component Analysis/Empirical Orthogonal Function (PCA/EOF) method, have not been implemented for the analysis and modelling of temporal mass variations within the Earth’s system over the area of Poland. The aim of this contribution is to analyse and model temporal variations of geoid heights obtained from GRACE mission data over the area of Poland using the PCA/EOF method. Temporal variations of geoid heights were obtained from the latest release, i.e. release five, of monthly GRACE-based Global Geopotential Models. They can reach the level of 10 mm. The PCA modes and their corresponding EOF loading patterns were estimated using two different algorithms. The results obtained revealed that significant part of the signal of temporal variations of geoid heights over Poland can be obtained from the first three PCA modes and EOF loading patterns. They demonstrate the suitability of the PCA/EOF method for analysing and modelling temporal variations of geoid heights over the area investigated.PubDate: 2017-09-25DOI: 10.1007/s40328-017-0206-8